Current generation Adenovirus (Ad) vector vaccines deleted at the E1 or the E1, E3 regions have resulted in experimental potential to immunize against a variety of infectious diseases such as HIV. These Ad vectors permit the delivery of genes, which express proteins that stimulate the immune system. An advanced generation of Ad vectors with unique deletions of the E1 and E2b region (E2b encodes the viral DNA polymerase (pol) and the preterminal protein (pTP) has previously been described. The deletion of these genetic regions renders the Ad5 [E1-, E2b-] virus completely replication incompetent. The new human Ad5 [ E1-,E2b-] vectors have several advantages. Ad viral DNA replication is significantly diminished and the removal of the E2b region results in a 10,000-fold reduction in the production of Ad late gene products, further reducing the potential of Ad encoded viral proteins from impacting host immune responses. Moreover, use of Ad5 [E1-, E2b-] vectors have been shown to have decreased cytotoxicity. The Ad5 [E1-, E2b-] vectors can also lead to an increased quantity and sustained expression of inserted transgenes. These characteristics of Ad5 [E1-, E2b] vectors suggest that they are superior to Ad5 [ El-] vectors. In light of these advantages, our strategy is to employ the use of Ad5 [E1-, E2b-] vectors as a new platform for vaccine based vectors. Specifically, we chose to use this new Ad5 platform as a vaccine platform for HIV-1. Our Phase 1 goal to investigate Ad5 [E1-, E2b-] vectors was very successful. Multiple immunizations induced robust immunologic responses to transgene products. We observed that animals could be immunized with one antigen and then subsequently immunized with a second differing antigen in the presence of Ad5 immunity. In comparison with the current generation Ad5 [E1-] vector, our [E1-, E2b-] vector induced higher levels of interferon-? and lL-2 secreting lymphocytes both in Ad5 naive and Ad5 immune. Studies also demonstrate that animals could be immunized with a triad mixture of Ad5 [E1-, E2b-] gag, nef, pol. Our analysis of samples from our initial vaccine trial in NHPs suggest that they can be successfully immunized against the HIV gag protein in the presence of pre-existing Ad5 hyper immunity. In Phase II, studies will be performed in mice and NHPs to further develop the vaccination regimen. The Aims of the Phase II study are to (1) prepare SIV and human Ad5 [E1-, E2b-]-gag, pol, nef vaccine platforms. (2) determine the optimal frequency and optimal route of triad vaccination in mice by investigating immunizations on a weekly, bi-weekly and monthly schedule and also compare intradermal, intramuscular, intraperitoneal and intravenous routes of immunization with a triad mix of Ad5 [E1-, E2b-]-gag/pol/nef vectors. (3) determine the duration of transgene expression in vivo. (4) test safety and immunogenicity of the triad vaccine in Ad5 na[unreadable]ve and Ad5 immune NHP, and (5) perform SIV challenge studies of vaccinated NHPs. Etubics will perform these pre-clinical studies to advance this new vaccine platform into clinical trials. PUBLIC HEALTH RELEVANCE: With approximately 5,000 new HIV-1 infections occurring daily and the failure of the Merck 'STEP" HIV vaccine trial, the need for a viable HIV-1 vaccine is urgent. During this study, we will further develop our advanced adenoviral vector delivery system for HIV vaccines. The system is needed to break through the barrier presented by vaccinees who have had prior adenovirus infections which includes many humans worldwide.